Oxygen sensor

Abstract

A protective layer of zirconia particles having particle sizes of 0.5-5 μM is provided on a surface of an electron-conducting layer of an oxygen sensor at a side of a gas whose oxygen concentration is to be detected to a thickness of 4-100 μM by bonding zirconia particles to one another and the first electron-conducting layer by 10-30% by weight of a high melting point adhesive, such as powders of borosilicate glass, based on total weight of the zirconia particles.

What is claimed is: 
     
       1. An oxygen sensor, which comprises a zirconia layer for transmitting oxygen ions therethrough, provided to separate a gas whose oxygen concentration is to be detected from a reference gas; a first electron-conducting layer having a catalytic action, provided on a surface of the zirconia layer on the side of the gas whose oxygen concentration is to be detected; a second electron-conducting layer for ionizing oxygen molecules in the reference gas and taking the oxygen ions into the zirconia layer, provided on a surface of the zirconia layer on the side of the reference gas; and a protective layer of zirconia particles provided on the outer surface of the first electron-conducting layer, said zirconia particles being bonded to one another and to the first electron-conducting layer by a high melting point adhesive comprising a powder of borosilicate glass, water glass having a melting point of 900° C. or higher, a phosphate, or cement, whereby an electrical signal is generated between the first and the second electron-conducting layers in accordance with the difference in oxygen concentrations between the gas whose oxygen concentration is to be detected and the reference gas. 
     
     
       2. An oxygen sensor according to claim 1, wherein particle sizes of the zirconia particles for the protective layer are 0.5-5 μM. 
     
     
       3. An oxygen sensor according to claim 1, wherein thickness of the protective layer is 4-100 μM. 
     
     
       4. An oxygen sensor according to claim 1, wherein 10-30% by weight of the high melting point adhesive, based on total weight of the zirconia particle is used for the protective layer. 
     
     
       5. An oxygen sensor, which comprises a zirconia layer for transmitting oxygen ions therethrough, provided to separate a gas whose oxygen concentration is to be detected from a reference gas; a first electron-conducting layer having a catalytic action, provided on a surface of the zirconia layer on the side of the gas whose oxygen concentration is to be detected; a second electron-conducting layer for ionizing oxygen molecules in the reference gas and taking the oxygen ions into the zirconia layer, provided on a surface of the zirconia layer on the side of the reference gas; and a protective layer of zirconia particles having particle sizes of 0.5-5 μM to a thickness of 4-100 μM provided on the outer surface of the first electron-conducting layer, said zirconia particles being bonded to one another and to the first electron-conducting layer by 10-30% by weight of a high melting point adhesive, based on total weight of the zirconia particles, comprising a powder of borosilicate glass, water glass having a melting point of 900° C. or higher, a phosphate, or cement, whereby an electrical signal is generated between the first and second electron-conducting layers in accordance with a difference in oxygen concentration between the gas whose oxygen concentration is to be detected, and the reference gas.